The present invention relates to a polyalkylene oxide having an unsaturated group at its polymer end or ends, having any desired molecular weight, and having a narrow distribution of molecular weight.
There have been known polyalkylene oxides having unsaturated groups at both ends of the polymers. These polyalkylene oxides having unsaturated groups at their polymer ends are used as rubber materials by curing them alone, or are used as crosslinkable modifiers for blending with other polymers. Further, as disclosed in U.S. Pat. No. 3,971,751, polyalkylene oxides where unsaturated end groups are converted to other more active functional groups such as hydrolyzable silyl groups can be employed in various uses as a telechelic liquid rubbers.
In the polyalkylene oxides, polyoxypropylenes having an unsaturated end group can be prepared by using a polyoxypropylene obtained by a usual anion-polymerization in the presence of KOH as a starting material, converting the hydroxyl group of the polyoxypropylene to an alkoxide groups by using metal sodium and the like, and then reacting with a halogenated compound which contains an unsaturated group such as allyl chloride. According to the usual anion-polymerization in the presence of KOH catalyst, however, it is difficult to produce a polyoxypropylene having a narrow distribution of molecular weight. It is also difficult to produce a polyoxypropylene having a number average molecular weight of not less than 3,000, because chain transfer reaction occurs to the propagating chain end against propylene oxide monomer. Therrefore the particular process is required for producing a polyoxypropylene which has a number average molecular weight of not less than 3,000 and has unsaturated groups at its both ends. According to such a process, for example, as disclosed in U.S. Patent No. 3,951,888, a polyoxypropylene having unsaturated groups at its both ends is produced by converting the hydroxyl groups of a polyoxypropylene to alkoxide groups with metal sodium or the like, reacting with a polyhalogenated compound such as methylene chloride to increase the molecular weight, and then reacting with an active halogen-containing compound having an unsaturated group. It is difficult, however, to precisely prepare a polymer having a desired molecular weight according to those conventional processes. Further, the distribution of molecular weight of the polymer product becomes wide because the chain propagation reaction caused by the polyhalogenated compound occurs ununiformly. When using a polyalkylene oxide having a wide distribution of molecular weight, there is a problem that tensile properties of the cured produce are inferior.
The present inventors found that living polymerization of propylene oxide can be carried out by using a complex catalyst of the reaction product of an organoaluminium compound with a porphyrin compound, and that a polymer having a narrow distribution of molecular weight can be prepared according to such a process (T. Aida eta l, "Makromol. Chem." 182, 1073-1079 (1981). AS a result of the present inventors' further study, it has been found that when using the above new complex catalyst, a polyoxypropylene having unsaturated groups at its ends, and having any desired molecular weight, especially a relatively high molecular weight of not less than 4,000, and also having a narrow distribution of molecular weight can be easily prepared.